01 -
Slice Yukon Gold potatoes into 1/8-inch rounds and place them in a bowl of water to prevent discoloration.
02 -
Preheat the oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish and set aside.
03 -
In a large skillet over medium-high heat, cook ground beef, diced onion, and minced garlic. Break up the beef while cooking and sauté until browned. Drain excess fat.
04 -
In a medium bowl, whisk together cream of mushroom soup, half and half, onion powder, kosher salt, and black pepper until completely smooth.
05 -
Layer one third of the sliced potatoes evenly on the bottom of the prepared baking dish. Top with one third of the beef mixture, 3/4 cup shredded Colby Jack cheese, and one third of the sauce. Repeat this layering for the second layer with the next third of ingredients. For the final layer, arrange remaining potatoes and beef, pour over the remaining sauce, and finish with 1.5 cups cheese evenly distributed on top.
06 -
Cover the baking dish tightly with aluminum foil and bake for 1 hour and 10 minutes.
07 -
Remove foil and continue baking uncovered for 20 minutes, until the top is golden and bubbling.
08 -
Allow the casserole to rest for 15 minutes before slicing and serving.